Topic: Will a cb350 rear drum give sufficient stopping power to a cb750 racer.

[peejke]

Hi ,
I'm building a '75 Cb750 racer for the BElgium street circuits. In front I'm using a twin disk setup. But to keep the turning weight as low as possible I was thinking to put a cb350 rear drum in the back. I would reline it with racing liner. Do you guys think this is sufficient and will it has the correct wide to go fit the 750 rear ??

[peejke]

I mean , is the total wide of the drum including the spacers the same for the 350 and 750 , so it will fit the 750 swingarm without chain lining issues.

[gschuld]

I believe Brent Waller is running a cb350 rear drum on his super fast cb500 based racer.  It's a very light bike with a modest weight rider (s), so take that into account.  The cb500/550 rear drum is lighter than a cb750 by a good bit, and might be the safer route. 

George

[Justind97]

I think it would work just fine.

Actually using the rear brake while racing is debatable.   I certainly don't.

I was in a similar boat.  I had a cb400f rear hub, 4.75kg (10.45lbs) and cb550 rear hub 6.75kg (14.85lbs) 

It shouldn't be an issue, however make sure the mounting points for the gear and strong enough to withstand the hp difference 

[vfourfreak]

I'd be less worried about the braking effort and more by the transmission side of things. As in will the CB350 cush drive take the power delivered by the bigger motor ? The case of Brent's racer quoted above may go some way to assure one on that point, but I think it would be best to be sure.

Kev

[bwaller]

I use the rear brake for stability on occasion, so I don't care that is isn't strong. The four cush units are adequate, but the fact there are only four sprocket mounting studs may be a concern depending on what you expect for power. In my case 72 at the wheel. I did make a sprocket spacer/carrier that runs on a bearing which helps.

[peejke]

thanks for the helpful replies. Do you maybe have a picture of the sprocket spacer/carrier

[bwaller]

First I machined the original "nose" off the hub. Then the bearing in the new carrier has a large enough ID to allow a spacer to fit by interference so when the axle is tightened the carrier is held square with the hub. Helicoils in the carrier, original studs used to locate the carrier, and bolts for the sprocket.